Combining Ability Analysis for Bacterial Leaf Spot Resistance, Leaf Yield, and Agronomic Traits in Mulberry Clones

Combining ability effects for disease resistance, yield, and agronomic traits help in devising appropriate breeding strategies. Bacterial leaf spot (BLS) [Xanthomonas campestris pv.mori] is a destructive foliar disease of mulberry (Morus spp.). We evaluated crosses of useful mulberry clones to select good general combiners for resistance to BLS and to determine the genetics of important agronomic traits for mulberry improvement. Combining ability of six parents was estimated following a line × tester mating design. Established full-sib segregating progenies (440) derived from eight crosses, along with parents, were field-evaluated for leaf yield, agronomic traits, and resistance to BLS across two years. Significant negative (p < 0.01) general combining ability (GCA) effect of disease severity was found in genotype M. rotundiloba, which is desirable for BLS resistance; whereas significant positive GCA for leaf yield was observed in two parents, namely, M. multicaulis and C-2016. Moderately high narrow-sense heritability estimates (≥0.46), continuous frequency distributions, and moderately high genetic gains (19%–22%) were observed for traits such as primary shoot length, internodal distance, and petiole width. M. rotundiloba appeared to be a good general combiner for BLS resistance. Selection for primary shoot length, nodal distance, and petiole width should be effective for improving mulberry.